Battery pack and its charging/discharging method

ABSTRACT

Disclosed are a battery package and a method for charging and discharging secondary batteries including nickel hydrogen batteries by refreshing and suppressing inactivity of the batteries. More concretely, battery package ( 101 ) comprises a group of batteries having a plurality of connected secondary batteries, each forming a unit battery, a plurality of sensors for detecting a temperature and a voltage, a display device for displaying a condition of the group of batteries, a switch for controlling charge and discharge of the group of batteries, and an operational control circuit ( 4 ) for generating a signal based on signals input from the plurality of sensors to make the display device display the condition of the group of batteries and to activate the switch, wherein the battery package ( 101 ) is provided with refreshing demand display device ( 13 ) for displaying a need to initiate a refreshing charge and discharge, and it uses the method of carrying out the refreshing charge and discharge automatically when a recovery voltage of the secondary batteries does not exceed a predetermined voltage after a lapse of a predetermined time from a moment when the secondary batteries come to a final discharge voltage. This invention can thus carry out the refreshing charge and discharge even for secondary batteries that become inactive after having been left unused for a long time.

TECHNICAL FIELD

The present invention relates to a battery package comprising asecondary battery such as an alkaline storage battery, and a batterycontrolling method such as a charging and discharging method foreffective use of the battery package. In particular, the inventionrelates to a method of controlling a battery during charging anddischarging the battery package comprising the secondary batteryconsisting of the alkaline storage battery such as a nickel hydrogenbattery used in the battery package, as well as a method of makingeffective use of a capacity of the secondary battery contained in thebattery package.

BACKGROUND ART

The remarkable progress in the technology of electronics in recent yearshas made possible downsizing and weight reduction of many electronicapparatuses, and it has resulted in a rapid advancement of cordless andportable operation of the apparatuses. With the advancement of theseapparatuses, there is an increased demand for small and lightweightbatteries (i.e., storage batteries, or secondary batteries) of highenergy density, useful as power supplies for the electronic apparatuses.These batteries have been used as power supplies of numerous productsincluding power sources of electric tools, backup power supplies, andthe like. Nickel cadmium battery is one kind of these batteries (i.e.,secondary batteries) that have been hitherto used widely as the powersupplies. However, because of the increase in demand of high capacity,and worldwide concern of environmental problems, nickel hydrogenbatteries have been developed recently as new products to replace thenickel cadmium batteries, and they are now spreading widely into themarket.

In a battery package comprising any of these secondary batteries,however, there was a tendency in the past that a battery voltagedecreases due to self-discharge and the like of the battery if it isleft unused for a long period of time, in addition to a problem that acapacity of the battery decreases because the battery becomes inactiveduring repeated recharges and discharges, which eventually makes thebattery unable to maintain a sufficient capacity. A cause of theinactivity of the battery is that the repeated recharges and dischargescause reduction of oxide in a positive electrode, and oxidization ofhydroxide in a negative electrode. To clear the inactivity resulted fromthe above causes, the battery needs refreshing charge and discharge.

A number of methods were contrived to carry out the refreshing chargeand discharge. To cite a few examples, one method is to give a display,which indicates a need to carry out a refreshing discharge by counting anumber of recharges or discharges, and another method proposed is toincrease the number to be counted according to a temperature of thebattery and decreases a number of recharges before initiating therefreshing process since the battery tends to enhance the memory effectwhen the battery temperature is high (refer to an Unexamined JapanesePatent Application, Publication No. 2001-126776).

FIG. 3 is a block diagram of a battery package, prepared for the purposeof describing an example of such conventional methods of displaying acapacity of secondary battery used for the refreshing charge anddischarge. In FIG. 3, packaged battery 101 (or, a battery package) usedfor the method of displaying a capacity comprises: secondary battery 103of a type a dischargeable capacity of which decreases due to the memoryeffect as recharge and discharge are repeated; remaining capacitydisplay device 113 for displaying a remaining capacity of the batterypackage by lighting up a corresponding number of indicator lamps among aplurality of them, or by using a liquid crystal display and the like;current detection circuit 114 for detecting a charging current and adischarge current of the battery; temperature sensor 104 placed incontact with secondary battery 103 for detecting a temperature ofsecondary battery 103; switch 106 composed of a semiconductor switchingelement such as an FET or a transistor, and connected between secondarybattery 103 and output terminal 105; control circuit 107 for computingthe remaining capacity and a timing of refreshing, in addition tocontrolling the switch 106; refreshing circuit 108 for dischargingsecondary battery 103 nearly completely to cancel the memory effect ofthe secondary battery 103; and refreshing display device 109 fordisplaying the refreshing operation.

Temperature sensor 104 in packaged battery 101 detects a temperature ofsecondary battery 103, and inputs a temperature signal to controlcircuit 107. Switch 106 is controlled by control circuit 107 in a mannerthat it turns on when secondary battery 103 needs charging, and it turnsoff when secondary battery 103 is fully charged to prevent overchargingof the secondary battery 103. In addition, switch 106 is controlled alsoby control circuit 107 in a manner to turn on when secondary battery 103is discharged, but it is turned off again when secondary battery 103 iscompletely discharged to prevent the secondary battery 103 from beingover-discharged.

Control circuit 107 is provided with counter 110 for counting a numberof recharges of secondary battery 103, as well as operational circuit111. Operational circuit 111 computes a timing to initiate a refreshingoperation by comparing a counted value of counter 110 with a presetvalue, controls switch 106 by detecting a charging condition anddischarging condition of secondary battery 103, and computing aremaining capacity from a charging current and a discharging current.Counter 110 counts the number of recharges by adding one to the countedvalue whenever recharging is made, and resets the counted value to zerowhen the secondary battery 103 is refreshed. Counter 110 also checks thecharging condition by detecting a change in voltage across outputterminals 105, when a charger (not show in the figure) is connected forcharging secondary battery 103. Current detection circuit 114 isconnected between secondary battery 103 and one of output terminals 105,and a voltage produced at both ends of this current detection circuit114 is used to detect a charging current as well as a dischargingcurrent. Operational circuit 111 compares the number of recharges ofpackaged battery 101, or the counted value of counter 110, with thepreset value, and informs of a timing of the refreshing operation whenthe counted value becomes equal to or exceeds the preset value. However,operational circuit 111 is controlled according to a program so that itdetermines the timing of refreshing operation after correcting thecounted value of counter 110 based on the battery temperature, insteadof comparing the counted value directly with the preset value, since thesecondary battery 103 generally has a tendency of enhancing the memoryeffect when its temperature rises, and losing the memory effect when thetemperature falls.

During the refreshing discharge in which the secondary battery isdischarged from the fully charged condition to a final dischargevoltage, the conventional method of this kind for displaying a capacityof the secondary battery comprises the steps of computing a full-chargecapacity according to an integrated value of discharge current,correcting a remaining capacity by using the computed full-chargecapacity, and further correcting the remaining capacity thereafter byusing the counted value. Additionally, this method comprises the stepsof counting a number of recharges of the secondary battery, anddisplaying a need of refreshing operation when the counted number ofrecharges reaches a predetermined number. The method further comprisesthe steps of detecting a battery temperature, and reducing the number ofrecharges to be counted before initiating a refreshing operation of thesecondary battery.

In this method of counting a number of recharges, however, there was adrawback in which a need for the refreshing charge and discharge is notdisplayed when the battery become inactive as a result of it having beenleft unused for a long period of time, since the refreshing charge anddischarged is programmed to be carried out according to the number ofrecharges or discharges, irrespective of the actual charge and dischargecondition of the battery. To put it more concretely, consider an exampleof charge and discharge system which is designed to carried out arefreshing charge and discharge every after 50 times of recharging anddischarging. After the battery has undergone 25 times of recharging anddischarging process, for instance, it is still due to normal rechargeand discharge without being subjected to another refreshing charge anddischarge even if it is left unused for a long time without beingrecharged or discharged and becomes inactive, because the number ofrecharge counts has not reached 50 times. This is a problem to beresolved, since a resulting increase in an internal resistance of thebattery due to enhancement of the memory effect and inactive conditionof the battery makes it not capable of discharging a sufficiently largecurrent, and prevents it from being used effectively.

The present invention was contrived to solve the above problems in theconventional method of carrying out the refreshing charge and dischargeof the secondary battery contained in the battery package. It is thus anobject of this invention to provide a technique which makes refreshingcharge and discharge possible even for the secondary battery that hasbeen left unused for a long time and become inactive, and to make thesecondary battery effectively useful.

SUMMARY OF THE INVENTION

To achieve the above object, a battery package of this inventioncomprises: a group of batteries having a plurality of connectedsecondary batteries, each forming a unit battery; a plurality of sensorsfor detecting a temperature and a voltage; a display device fordisplaying a condition of the group of batteries; a switch forcontrolling charge and discharge of the group of batteries; and anoperational control circuit for generating a signal based on signalsinput from the plurality of sensors to make the display device displaythe condition of the group of batteries, and to activate the switch,wherein this structure is provided further with a refreshing demanddisplay device for displaying a need to initiate a refreshing charge anddischarge if a recovery voltage of the secondary batteries does notexceed a predetermined voltage after a predetermined time has elapsedfrom a moment when the batteries come to a final discharge voltage.

Another battery package of this invention comprises: a group ofbatteries having a plurality of connected secondary batteries, eachforming a unit battery; a plurality of sensors for detecting atemperature and a voltage; a display device for displaying a conditionof the group of batteries; a switch for controlling charge and dischargeof the group of batteries; and an operational control circuit forgenerating a signal based on signals input from the plurality of sensorsto make the display device display the condition of the group ofbatteries, and to activate the switch, wherein the operational controlcircuit has a non-detecting timer for preventing the sensors fromdetecting the voltage during another predetermined time period frombeginning of the charge, the operational control circuit counts a numberof times in which the voltage of the batteries exceeds a preset voltagewithin the another predetermined time period, and the battery package isprovided further with a refreshing demand display device for displayinga need to initiate a refreshing charge and discharge when the countednumber reaches a predetermined number.

Still another battery package of this invention comprises: a group ofbatteries having a plurality of connected secondary batteries, eachforming a unit battery; a plurality of sensors for detecting atemperature and a voltage; a display device for displaying a conditionof the group of batteries; a switch for controlling charge and dischargeof the group of batteries; and an operational control circuit forgenerating a signal based on signals input from the plurality of sensorsto make the display device display the condition of the group ofbatteries, and to activate the switch, wherein the operational controlcircuit has a non-detecting timer for preventing the sensors fromdetecting the voltage during another predetermined time period frombeginning of the charge, the operational control circuit counts a numberof times in which the voltage of the batteries exceeds a preset voltagewithin the another predetermined time period, and the battery package isprovided further with a refreshing demand display device for displayinga need to initiate a refreshing charge and discharge in any of eventsthat the counted number reaches a predetermined number, and a recoveryvoltage of the batteries does not exceed a predetermined voltage after apredetermined time has elapsed from a moment when the batteries come toa final discharge voltage.

Furthermore, the battery package of this invention comprises any of astructure having a refreshing demand display device for displaying aneed to initiate a refreshing charge and discharge if the recoveryvoltage of the secondary batteries does not exceed 1.15 volt after oneday or longer time has elapsed from a moment when the batteries come tothe final discharge voltage; another structure having secondarybatteries, each comprising an alkaline storage battery provided with apositive electrode mainly composed of a nickel oxide, a negativeelectrode, a separator, and an alkaline electrolyte; still anotherstructure having the batteries provided with a negative electrode formedof a hydrogen storage alloy; and yet another structure having atemperature sensor for detecting a temperature of the secondarybatteries and an operational control circuit for computing a rate oftemperature change according to the detected temperature, and generatinga signal for termination of the charge and delivering it to a switch forcontrolling charge and discharge of the group of batteries when the rateof temperature change exceeds a preset range.

To further achieve the above object, a method of charging anddischarging battery of this invention pertains to a battery packagecomprising: a group of batteries having a plurality of connectedsecondary batteries, each forming a unit battery; a plurality of sensorsfor detecting a temperature and a voltage; a display device fordisplaying a condition of the group of batteries; a switch forcontrolling charge and discharge of the group of batteries; and anoperational control circuit for generating a signal based on signalsinput from the plurality of sensors to make the display device displaythe condition of the group of batteries, and to activate the switch,wherein the method comprises the step of carrying out a refreshingcharge and discharge if a recovery voltage of the secondary batteriesdoes not exceed a predetermined voltage after a predetermined time haselapsed from a moment when the batteries come to a final dischargevoltage.

Another method of charging and discharging battery of this inventionpertains to a battery package comprising: a group of batteries having aplurality of connected secondary batteries, each forming a unit battery;a plurality of sensors for detecting a temperature and a voltage; adisplay device for displaying a condition of the group of batteries; aswitch for controlling charge and discharge of the group of batteries;and an operational control circuit for generating a signal based onsignals input from the plurality of sensors to make the display devicedisplay the condition of the group of batteries, and to activate theswitch, wherein the method comprises the steps of preventing the sensorsfrom detecting the voltage by means of a non-detecting timer provided inthe operational control circuit; counting a number of times in which thevoltage of the batteries exceeds a preset voltage within anotherpredetermined time period by means of the operational control circuit;and carrying out a refreshing charge and discharge when the countednumber reaches a predetermined number.

Still another method of charging and discharging battery of thisinvention pertains to a battery package comprising: a group of batterieshaving a plurality of connected secondary batteries, each forming a unitbattery; a plurality of sensors for detecting a temperature and avoltage; a display device for displaying a condition of the group ofbatteries; a switch for controlling charge and discharge of the group ofbatteries; and an operational control circuit for generating a signalbased on signals input from the plurality of sensors to make the displaydevice display the condition of the group of batteries, and to activatethe switch, wherein the method comprises the steps of preventing thesensors from detecting the voltage by means of a non-detecting timerprovided in the operational control circuit; counting a number of timesin which the voltage of the batteries exceeds a preset voltage withinanother predetermined time period by means of the operational controlcircuit; and carrying out a refreshing charge and discharge in any ofevents that the counted number reaches a predetermined number, and arecovery voltage of the batteries does not exceed a predeterminedvoltage after a predetermined time has elapsed from a moment when thebatteries come to a final discharge voltage.

In addition, the method of charging and discharging battery of thisinvention comprises the step of carrying out a refreshing charge anddischarge if the recovery voltage of the secondary batteries does notexceed 1.15 volt after one day or longer time has elapsed from a momentwhen the batteries come to the final discharge voltage.

Furthermore, the method of charging and discharging battery of thisinvention comprises any of the steps of charging the battery up to 90 to120% of an initial capacity with a current of 5.0 It or less, andfurther charging up to 150 to 200% with a current of 2.0 It or less fora given duration controlled by the timer function provided in theoperational control circuit during the refreshing charge and discharge,where “It” denotes a rated battery capacity; detecting a temperature ofthe secondary batteries with the sensor, computing a rate of temperaturechange according to the detected temperature by means of the operationalcontrol circuit, and delivering a signal for termination of the charge.to the switch for controlling-charge and discharge of the group ofbatteries when the rate of temperature change exceeds a preset range;presetting the rate of temperature change to 0.5 to 4.0° C./min;presetting the rate of temperature change to 1.0 to 3.0° C./min; andcarrying out the charge and discharge by any of a constant-currentcharging and discharging method, a constant-voltage charging anddischarging method, and a combination of the constant-current chargingand discharging method and the constant-voltage charging and dischargingmethod.

In the above structure, the battery voltage decreases or the internalresistance increases if the unit batteries constituting the secondarybatteries included in the battery package are inactive and their voltageis 1.15 volt or less. This is a phenomenon caused by decrease inreactivity of the electrodes and loss of uniformity in distribution ofthe electrolytic solution inside the batteries, which produces oxygenand hydrogen gases due to decomposition of water as an adverse reactionbesides the original charge and discharge reactions, and these gasesaccelerate degradation of the batteries and shortens their serviceablelife. The refreshing charge and discharge, when carried out in a timelymanner, can reactivate the electrodes and suppress generation of theoxygen and hydrogen gases, thereby prolonging the serviceable life ofthe batteries.

When the batteries are charged and discharged with a large current insuch instances that a charging voltage is increased abruptly during theinitial stage of charging and the batteries are discharged rapidly, thelarge current promotes the adverse reaction and increases an amount ofgases generated inside the batteries, which accelerates degradation ofthe batteries and further shortens the life span of these secondarybatteries. For the above reason, this invention suppresses thegeneration of gases by charging the batteries up to 90 to 120% of theinitial capacity at first with a current of 5.0·It or less, then up to150 to 200% with a current of 2.0·It or less, and discharging themthereafter. This method can thus activate the electrodes, and prolongthe serviceable life of the secondary batteries.

In addition, since the invented method comprises the step of resettingthe remaining capacity every after the refreshing charge and dischargeof the secondary batteries, this method can rectify a reduction of thecapacity attributable to the decrease in charging efficiency of thebattery package due to inactivity of the electrodes, thereby realizingefficient charging and discharging.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a battery package for reference purpose inconnection with description of a method of displaying a capacity usedfor refreshing charge and discharge of a secondary battery according tothe present invention;

FIG. 2(a) is a longitudinal sectional view of an alkaline storagebattery contained in the battery package of this invention, as sectionedvertically in a plane along the center of a positive electrode terminalof the battery;

FIG. 2(b) is a cross sectional view of the alkaline storage batterycontained in the battery package of this invention, as sectioned along aline A-A′ shown in FIG. 2(a); and

FIG. 3 is a block diagram of a battery package for reference purpose inconnection with description of a conventional method of displaying acapacity used for refreshing charge and discharge of a secondarybattery.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to the accompanying drawings, description will be providedhereinafter of a battery package equipped with a secondary battery and amethod of carrying out refreshing charge and discharge according to apreferred embodiment of the present invention.

Shown in FIG. 1 is a block diagram of a battery package for use inconnection with the following discussion of a method of displaying acapacity used for the refreshing charge and discharge of the secondarybattery according to the present invention. In FIG. 1, packaged battery101 (may also be called “battery package”) contains battery voltagedetector 1 for monitoring a voltage of secondary battery 12 constitutingthe packaged battery 101, charge and discharge current detector 2 fordetecting an electric current across shunt resistor 11 connected tosecondary battery 12 and determining whether the battery is beingcharged or discharged, and a number of sensors such as temperaturesensor 3 made of a thermistor or the like for detecting a temperature.Operational control circuit 4 comprising a semiconductor device such asa microcomputer IC or the like receives detected signals from the groupof sensors, and delivers a signal to charge interruption controller 5comprising a switching device such as an FET to regulate a chargingcurrent by means of charging current interrupter 6 also composed of aswitching device such as an FET. Operational control circuit 4 sendsanother signal to abnormality display device 7 comprising an LED or thelike device for indication of an abnormality when it determines presenceof the abnormality in temperature, etc based on data on a batterytemperature, a rate of change of the temperature, and the like deliveredfrom temperature sensor 3.

Furthermore, operational control circuit 4 compares the battery voltageread by battery voltage detector 1 with a predetermined value ofvoltage, and outputs a signal to refreshing demand display device 13comprising an LED, for instance, when the voltage is smaller than thepredetermined value, to display the need to initiate a refreshing chargeand discharge. According to this display,. a user turns on refreshingswitch 15 to send a signal from operational control circuit 4 to chargeinterruption controller 5, which in turn performs switching control ofcharging current interrupter 6 to carry out the refreshing charge.Packaged battery 101 also comprises refreshing discharge circuit 14 forcarrying out the refreshing discharge, and discharge circuit interrupter8 comprising a switching device for interrupting the discharge inresponse to a signal from operational control circuit 4.

If the secondary battery is inactive, it shows a phenomenon in which thevoltage rises rapidly immediately after the start of a charging process,but this rapid rise soon subsides and the voltage again increasesgradually as the charging process advances. In packaged battery 101 usedfor the refreshing charge and discharge of the secondary batteryaccording to this exemplary embodiment of the invention, operationalcontrol circuit 4 is provided with a non-detecting timer (not shown) foravoiding the circuit 4 from detecting the rapid rise of voltage of thesecondary battery during a predetermined time period (non-detectingtime) in the beginning of the charging process in order to preventoperational control circuit 4 from interrupting the charging process dueto its voltage control function, when battery voltage detector 1 detectsthe voltage and a rate of the voltage change resulting from the rapidrise of the voltage.

During this non-detecting time period, operational control circuit 4compares the battery voltages taken by battery voltage detector 1 with apredetermined voltage value, counts the number of times the batteryvoltage detector 1 read a lower battery voltage if the voltage value issmaller than the predetermined value, and outputs a signal to refreshingdemand display device 13 comprising an LED or the like, when the numberreaches a preset value, to display the need to initiate a refreshingcharge and discharge. In response to the indication of refreshing demanddisplay device 13, a refreshing discharge is also performed in this caseby means of refreshing discharge circuit 14 and discharge circuitinterrupter 8.

Operational control circuit 4 also sends other signals to any ofremaining capacity display device 9 and degradation detector 10comprising LED's, when necessary, to make a variety of displays. Here,any of the switching devices that constitute charge interruptioncontroller 5, charging current interrupter 6 and discharge circuitinterrupter 8 may be substituted by a semiconductor device such as anFET or a relay.

The method of this invention for refreshing charge and discharge of thebattery package composed of the secondary battery such as an alkalinestorage battery is intended to manage the secondary battery after itbecomes inactive by using a charge and discharge control circuit havingthe refreshing function. Description is now provided more concretely ofthis controlling method.

Battery package 101 comprises ten pieces of serially connected unitbatteries, each rated 3.5 Ah in capacity and 1.2V in voltage for acombined rating of 3.5 Ah and 12V used here as an example of thesecondary battery 12 composed of alkaline storage batteries. Thealkaline storage batteries used as the unit batteries for the secondarybattery 12 contained in this battery package 101 has a structure shownin FIG. 2. FIG. 2(a) is a longitudinal sectional view of the alkalinestorage battery contained in the battery package of this invention, assectioned vertically in a plane along the center of a positive electrodeterminal thereof, and FIG. 2(b) is a cross sectional view of the sanebattery as sectioned along a line A-A′ shown in FIG. 2(a).

In FIG. 2, electrode assembly 20 is prepared by sandwiching positiveelectrode plate 23 in a form of sheet strip composed mainly of a nickeloxide and negative electrode plate 24 also of a sheet strip form withseparators 25 of the same sheet strip form, each placed between theelectrode plates 23 and 24 in a manner to isolate them electrically,winding the assembly around a spool of a prescribed diameter into aspiral configuration, wrapping around them with an insulation tape tofix the wound configuration, and resistance-welding a metal collector ofsubstantially a circular shape to projecting portions 27 of the positiveand the negative electrode plates by using a bronze welding rod. Afterthe electrode assembly 20 bearing the metal collectors attached theretoby welding is inserted in metal case 26, metal collector 28 at thebottom side welded to projecting portions 27 under the negativeelectrode plate 24 is further welded electrically to a bottom surface ofmetal case 26 by a bronze welding rod inserted through a void space inthe center of electrode assembly 20 from where the spool has beenremoved, and a given amount of alkaline electrolyte is injected from anopening on top of metal case 26. After that, metal seal plate 22provided with a positive terminal 31 of a cap-like shape is inserted inthe top opening of metal case 26, lead wire 30 defining a collector tabis connected to a lower surface of metal seal plate 22, and finally thetop opening of metal case 26 and metal seal plate 22 are sealed togetherwith gasket 33 placed around a fringe between them to thus complete analkaline storage battery of the structure shown in FIG. 2 of thisexemplary embodiment of the invention. The secondary battery containedas a unit battery in the battery package of this invention needs not belimited to the alkaline storage battery of the structure shown in FIG.2, but it can be a nickel hydrogen battery which uses negative electrodeplate 4 composed of a base material coated with powder of hydrogenstorage alloy.

Referring again to FIG. 1, battery voltage detector 1 monitors a totalvoltage, or the sum of all secondary batteries contained in batterypackage 101 at all the time. When the secondary batteries contained inbattery package 101 ceases to discharge, the battery voltage startsrising gradually thereafter from. the final discharge voltage to therecovery voltage. It takes about 2 to 3 hours for the full recovery inthe faster cases, but a day or longer in other cases depending onconditions of the secondary batteries.

If the unit batteries composing secondary battery 12 contained inbattery package 101 become inactive and show a recovery voltage equal toor less than 1.15V after the lapse of a certain time from the end ofdischarge, the battery voltage decreases and an internal resistanceincreases. This is attributable to a fall in reactivity of theelectrodes, which causes uneven distribution of the electrolyticsolution inside the batteries, and produces oxygen and hydrogen gasesdue to decomposition of water as an adverse reaction besides theoriginal charge and discharge reactions. These gases acceleratedegradation of the batteries and shorten their serviceable life. Therefreshing charge and discharge, when carried out, can reactivate theelectrodes and suppress generation of the oxygen and hydrogen gases,thereby prolonging the serviceable life of the batteries.

More specifically, when the battery voltage (i.e., recovery voltage) ofthese unit batteries becomes 1.15V/cell or less after the lapse of oneor more days from the end of discharge, battery voltage detector 1 sendsa signal to operational control circuit 4 comprising the microcomputeror the like, and operational control circuit 4 in turn sends anothersignal to refreshing demand display device 13 to make it display. When auser pushes refreshing switch 15 upon finding the display indicating aneed for refreshing charge due to the decrease in battery capacity,operation control circuit 4 connected to the refreshing switch 15delivers a signal for initiation of the refreshing charge to chargeinterruption controller 5 comprising a switching device such as an FET.As a result, charge interruption controller 5 turns on a switch incharging current interrupter 6, also comprising a switching device suchas an FET, to start the charging process.

On the other hand, when the batteries are charged and discharged with alarge current in such instances that the charging voltage is increasedabruptly during the initial stage of the charging process and that thebatteries are discharged rapidly, the large current promotes the adversereaction and increases an amount of gases generated inside thebatteries, which accelerates degradation of the batteries and furthershortens the life span of these secondary batteries. In other words, theamount of gases increases rapidly when the batteries are overcharged,and this increase in the amount of gases also influences a magnitude ofthe charging current. It is a general practice that the batteries arecharged with a large current up to 120% of their capacity, and thecharge is continued with a reduced current thereafter (beyond 120%). Ingeneral, batteries can be charged with a large current only up to 120%,although this depends upon design of the batteries. It is difficult toreactivate the electrode plates sufficiently if the batteries are notovercharged properly. Since the negative electrodes, in particular, havea capacity 1.5 times that of the positive electrodes, these electrodeplates can not be reactivated unless the batteries are charged to atleast 1.5 times (150%) the charging capacity of the positive electrodes.On the other hand, overcharging in excess of two times (200%) thecapacity must be avoided since it deteriorates the batteriesconsiderably.

It is thus desirable to discharge the batteries after they are chargedup to 90 to 120% of the initial capacity at first with a current of5.0·It or less, then up to 150 to 200% with a current of 2.0·It or less.This method can thus activate the electrode plates while suppressinggeneration of the gases, and thereby it prolongs the serviceable life ofthe batteries. Here, symbol “It” denotes a value of rated capacity ofthe batteries, and charging and discharging current is generallyrepresented by a multiple of this value. If a battery has 1 Ah capacity,for instance, 1.0·It represents 1 ampere and 2.0·It represents 2amperes.

Battery package 101 of this invention is adaptable for receiving powerfrom any kind of charging power supply using any such method asconstant-current charging, constant-voltage charging, or a combinationof the constant-current charging and the constant-voltage charging,although FIG. 1 does not show the charging power supply to be connectedto terminals 16 of battery package 101.

Sensor 3 comprising a thermistor, for example, for monitoringtemperature is placed in the vicinity of the batteries to constantlycheck a temperature of the batteries. Normally, an NTC (i.e., negativetemperature coefficient) type thermistor is used as a suitable devicefor this temperature-monitoring sensor 3. In this invention, batteryvoltage detector 1 send a signal to operational control circuit 4comprising the microcomputer IC or the like device when a rate of changein temperature of the batteries exceeds a predetermined value, andoperational control circuit 4 in turn gives a command for termination ofthe charging operation to charge interruption controller 5 comprisingthe switching device such as an FET. This turns off the switch incharging current interrupter 6 also comprising the switching device suchas an FET, and the charge is thus terminated. It is desirable that therate of temperature change “ΔT” of the batteries is kept between 0.5 and4.0° C./min, since it requires a considerably long time for charging anddischarging process if it is smaller than 0.5° C./min, and itaccelerates degradation of the batteries substantially if larger than4.0° C./min. In consideration of working hours required for charging anddischarging properly as well as the serviceable life of the batteries,it is more desirable that the rate of temperature change “ΔT” of thebatteries is set between 1.0 and 3.0° C./min before interrupting thecharge. If the rate of temperature change “ΔT” of the batteries islarger than the above value, it means the batteries are charged ordischarged with a current equal to or exceeding 5.0·It. Since this leadsto an overcharge in excess of 120% of the initial capacity, it canresult in a large amount of gases generated inside the batteries, asdescribed previously in relation of the overcharge to generation of thegasses. This gives rise to a possibility of degrading the secondarybatteries and deteriorating the property affecting their serviceablelife. For this reason, the batteries are charged subsequently up to 150to 200% of the initial capacity by changing the charging current to2.0·It for a given duration of time controlled by the timer function(may be called timer charging) provided in operational control circuit 4comprising the microcomputer or the like. The timer charging makespossible to overcharge the batteries that have become inactive, and toreactivate them. In battery package 101 shown in FIG. 1, operationalcontrol circuit 4 actually counts the charging time. When the chargingtime is set to 30 minutes, for instance, operational control circuit 4comprising the microcomputer or the like sends a signal again to chargeinterruption controller 5 comprising the switching device such as an FETafter the lapse of 30 minutes, and charging current interrupter 6comprising the switching device such as an FET also turns off its switchto terminate the charging process.

The invention also realizes reduction of working man-hours in themanufacturing process by way of operating refreshing discharge circuit14 with operational control circuit 4 comprising the microcomputer orthe like, which has the refreshing function for automatically initiatingthe refreshing charge and discharge.

There are two methods of determining a remaining capacity, of which oneis a method of measuring a closed-circuit voltage during discharge, andthe other is a current integration method wherein time and current areadded up during charges and discharges. The current integration methodis desirable for adoption to this method of charging and discharging thesecondary battery of the invention, since the former method of measuringthe closed-circuit voltage is liable to rise a phenomenon similar to thememory effect, which impedes continuous monitoring of the correctcapacity of the battery.

In the case of charging an inactive battery, an internal resistance ofthe battery increases and temperature of the battery rises. Thisterminates the charging process before the battery is fully chargedbecause it decreases a charging efficiency, and reduces an apparentcapacity (i.e., remaining capacity), which causes premature functioningof the charging control. As described, there is an increase indifference between the actual capacity and the apparent capacity (i.e.,remaining capacity). In this case, it is necessary to reset theremaining capacity after refreshing the battery, and to display thecapacity again in order to correct the reduction in the capacity causedby the decrease in charging efficiency of the battery packageattributable to inactivity of the electrode plates, and this requires aspecial attention. In other words, the battery needs to be reactivated(i.e., refreshing charge and discharge, or resetting) to normalizeoperation of the charging control, and to make it terminate the chargingprocess when the battery is fully charged. Accordingly, the method ofcharging and discharging the secondary battery of this invention caneasily control the refreshing process by using a variety of displaydevices equipped in packaged battery 101. A remaining capacity metercapable of indicating the remaining capacity in five levels with LED'smay be an example of the display device suitable for use as remainingcapacity display device 9 shown in FIG. 1.

INDUSTRIAL APPLICABILITY

According to the present invention, the method of carrying outrefreshing charge and discharge of the secondary battery uses anoperational control circuit comprising a microcomputer or the like andthe refreshing function by means of various kinds of display devicessuch as a refreshing demand display device and switching devices toexecute the refreshing charge and discharge, thereby clearing inactivityof a variety of secondary batteries including alkaline storage batteriessuch as nickel hydrogen batteries, and making effective use of thebatteries. In addition, since this method of carrying out the refreshingcharge and discharge of the secondary battery of the invention isadaptable for receiving power from any kind of charging power supplythat uses any method such as constant-current charging, constant-voltagecharging, and a combination of the constant-current charging and theconstant-voltage charging, it can be adapted to many kinds ofapparatuses equipped with secondary batteries such as alkaline storagebatteries.

1. A battery package comprising: a group of batteries having a pluralityof connected secondary batteries, each forming a unit battery; aplurality of sensors for detecting a temperature and a voltage; adisplay device for displaying a condition of the group of batteries; aswitch for controlling charge and discharge of the group of batteries;and an operational control circuit for generating a signal based onsignals input from the plurality of sensors to make the display devicedisplay the condition of the group of batteries, and to activate theswitch, wherein the battery package is further provided with arefreshing demand display device for displaying a need to initiate arefreshing charge and discharge if a recovery voltage of the secondarybatteries does not exceed a predetermined voltage after a lapse of apredetermined time from a moment when the secondary batteries come to afinal discharge voltage.
 2. A battery package comprising: a group ofbatteries having a plurality of connected secondary batteries, eachforming a unit battery; a plurality of sensors for detecting atemperature and a voltage; a display device for displaying a conditionof the group of batteries; a switch for controlling charge and dischargeof the group of batteries; and an operational control circuit forgenerating a signal based on signals input from the plurality of sensorsto make the display device display the condition of the group ofbatteries, and to activate the switch, wherein the operational controlcircuit is provided with a non-detecting timer for preventing thesensors from detecting the voltage during a predetermined time periodfrom beginning of the charge, the operational control circuit counts anumber of times that the voltage of the batteries exceeds a presetvoltage within the predetermined time period, and further wherein thebattery package is provided with a refreshing demand display device fordisplaying a need to initiate a refreshing charge and discharge when thecounted number reaches a predetermined number.
 3. A battery packagecomprising: a group of batteries having a plurality of connectedsecondary batteries, each forming a unit battery; a plurality of sensorsfor detecting a temperature and a voltage; a display device fordisplaying a condition of the group of batteries; a switch forcontrolling charge and discharge of the group of batteries; and anoperational control circuit for generating a signal based on signalsinput from the plurality of sensors to make the display device displaythe condition of the group of batteries, and to activate the switch,wherein the operational control circuit is provided with a non-detectingtimer for preventing the sensors from detecting the voltage during apredetermined time period from beginning of the charge, the operationalcontrol circuit counts a number of times that the voltage of thebatteries exceeds a preset voltage within the predetermined time period,and further wherein the battery package is provided with a refreshingdemand display device for displaying a need to initiate a refreshingcharge and discharge in any of events that the counted number reaches apredetermined number, and a recovery voltage of the batteries does notexceed a predetermined voltage after another predetermined time haselapsed from a moment when the batteries come to a final dischargevoltage.
 4. The battery package according to one of claim 1 and claim 3,wherein the refreshing demand display device displays a need to initiatethe refreshing charge and discharge if the recovery voltage of thesecondary batteries does not exceed 1.15 volt after one day or longertime has elapsed from the moment when the batteries come to the finaldischarge voltage.
 5. The battery package according to one of claim 1 toclaim 3, wherein each of the secondary batteries comprises an alkalinestorage battery provided with a positive electrode mainly composed of anickel oxide, a negative electrode, a separator, and an alkalineelectrolyte.
 6. The battery package according to claim 5, wherein thenegative electrode comprises a hydrogen storage alloy.
 7. The batterypackage according to one of claim 1 to claim 3, wherein the temperaturesensor for detecting temperature detects a temperature of the secondarybatteries, and the operational control circuit computes a rate oftemperature change according to the detected temperature, and generatesand delivers a signal for terminating the charge to the switch forcontrolling the charge and discharge of the group of batteries, when therate of temperature change exceeds a preset range.
 8. A method ofcharging and discharging a battery in a battery package, the batterypackage comprising: a group of batteries having a plurality of connectedsecondary batteries, each forming a unit battery; a plurality of sensorsfor detecting a temperature and a voltage; a display device fordisplaying a condition of the group of batteries; a switch forcontrolling charge and discharge of the group of batteries; and anoperational control circuit for generating a signal based on signalsinput from the plurality of sensors to make the display device displaythe condition of the group of batteries, and to activate the switch, andthe method comprising the step of carrying out a refreshing charge anddischarge if a recovery voltage of the secondary batteries does notexceed a predetermined voltage after a predetermined time has elapsedfrom a moment when the batteries come to a final discharge voltage.
 9. Amethod of charging and discharging a battery in a battery package, thebattery package comprising: a group of batteries having a plurality ofconnected secondary batteries, each forming a unit battery; a pluralityof sensors for detecting a temperature and a voltage; a display devicefor displaying a condition of the group of batteries; a switch forcontrolling charge and discharge of the group of batteries; and anoperational control circuit for generating a signal based on signalsinput from the plurality of sensors to make the display device displaythe condition of the group of batteries, and to activate the switch, andthe method comprising the steps of: preventing the sensors fromdetecting the voltage by means of a non-detecting timer provided in theoperational control circuit; counting a number of times in which thevoltage of the batteries exceeds a preset voltage within a predeterminedtime period by means of the operational control circuit; and carryingout a refreshing charge and discharge when the counted number reaches apredetermined number.
 10. A method of charging and discharging a batteryin a battery package, the battery package comprising: a group ofbatteries having a plurality of connected secondary batteries, eachforming a unit battery; a plurality of sensors for detecting atemperature and a voltage; a display device for displaying a conditionof the group of batteries; a switch for controlling charge and dischargeof the group of batteries; and an operational control circuit forgenerating a signal based on signals input from the plurality of sensorsto make the display device display the condition of the group ofbatteries, and to activate the switch, and the method comprising thesteps of: preventing the sensors from detecting the voltage by means ofa non-detecting timer provided in the operational control circuit;counting a number of times in which the voltage of the batteries exceedsa preset voltage within a predetermined time period by means of theoperational control circuit; and carrying out a refreshing charge anddischarge in any of events that the counted number reaches apredetermined number, and a recovery voltage of the batteries does notexceed a predetermined voltage after another predetermined time haselapsed from a moment when the batteries come to a final dischargevoltage.
 11. The method of charging and discharging a battery accordingto one of claim 8 and claim 10, comprising the step of carrying out therefreshing charge and discharge if the recovery voltage of the secondarybatteries does not exceed 1.15 volt after one day or longer time haselapsed from a moment when the batteries come to the final dischargevoltage.
 12. The method of charging and discharging a battery accordingto one of claim 8 to claim 10, further comprising the steps of chargingthe battery up to 90 to 120% of an initial capacity with a current of5.0·It or less, and further charging up to 150 to 200% with a current of2.0·It or less for a given duration controlled by the timer functionprovided in the operational control circuit during the refreshing chargeand discharge, where “It” denotes a rated battery capacity.
 13. Themethod of charging and discharging a battery according to one of claim 8to claim 10, further comprising the steps of detecting a temperature ofthe secondary batteries with the sensor, computing a rate of temperaturechange according to the detected temperature by means of the operationalcontrol circuit, and delivering a signal for termination of the chargeto the switch for controlling the charge and discharge of the group ofbatteries when the rate of temperature change exceeds a preset range.14. The method of charging and discharging a battery according to claim13, wherein the rate of temperature change is preset to a range of 0.5and 4.0° C./min.
 15. The method of charging and discharging a batteryaccording to claim 13, wherein the rate of temperature change is presetto a range of 1.0 and 3.0° C./min.
 16. The method of charging anddischarging a battery according to one of claim 8 to claim 10,comprising the step of carrying out charge and discharge by any of aconstant-current charging and discharging method, a constant-voltagecharging and discharging method, and a combination of theconstant-current charging and discharging method and theconstant-voltage charging and discharging method.